In addition to endoscopes for medical and non-medical technical applications, whose viewing angle is parallel to the longitudinal axis of the endoscope shaft, endoscopes with other fixed viewing angles have been developed for some time. The viewing angle of an endoscope is understood here and hereinafter always to mean the direction facing from the distal end of the endoscope, in which an object is situated that appears in the center of the image recorded by means of the endoscope. In many applications, however, a fixed viewing angle is a disadvantage. In the worst case, for example during a medical procedure, the endoscope must be replaced numerous times. In such cases it is an advantage to use an endoscope with a viewing angle that can be selected or adjusted in situ.
To select or adjust the viewing angle, the distal end of the endoscope can comprise a movable light-diverting device on whose orientation the viewing angle of the endoscope is dependent. The light-diverting device includes, for example, a prism or mirror, whose orientation determines in which direction (with respect to the distal end of the endoscope) observed objects are situated, or from which direction light falling onto the distal end of the endoscope is switched into an observation beam path and/or is diverted onto a light-sensitive image sensor.
In constructing an endoscope with adjustable viewing angle, a whole range of requirements must be taken into account. In particular, to achieve a high light intensity, a light-diverting device with the greatest possible cross-section is desired. In addition, it is desirable to have the greatest possible angular range within which the viewing angle can be adjusted. At the same time, the distal end of an endoscope always has only a limited structural space available for the light-diverting device and its mobility. With increasing miniaturization or decreasing shaft cross-section, the available structural space becomes constantly smaller. Therefore new approaches are required in order to comply more closely with the requirements for constructing an endoscope.